A variety of data and services are transmitted and provided in an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) according to an asynchronous mobile communication system standard (3GPP). Examples of such data and services include system information transmitted through a Broadcast Channel (BCH), a control message transmitted through a Physical Downlink Control Channel (PDCCH), user traffic or a control message transmitted through a downlink/uplink Shared Channel (SCH), Broadcast/Multicast Service (MBMS) traffic or a control message transmitted through a downlink SCH or a downlink Multicast Channel (MCH), and an initial uplink control message transmitted through a Random Access Channel (RACH).
As a kind of broadcast/multicast service, the Multimedia Broadcast Multicast Service (MBMS) provides a streaming or background service to a plurality of UEs using a MBMS bearer service which is dedicated for a downlink. The term “broadcast/multicast service” or “MBMS” used in this disclosure can be replaced with other terms such as “point-to-multipoint service” or “Multicast and Broadcast Service (MBS)”. The MBMS is based on IP multicast, and thus terminals share resources required for data packet transmission and receive the same multimedia data. Accordingly, the MBMS can increase resource efficiency when more than a specific number of terminals are present in the same cell. The MBMS service is not associated with RRC connection, and thus even terminals in a sleep mode can receive the service.
The MBMS service is provided according to two modes, a broadcast mode and a multicast mode. One sender transmits data to all recipients in the broadcast mode and one or more senders transmit data to one or more specific recipients in the multicast mode. In the multicast method, the recipient needs to transfer the intention of receiving data to the network and can subscribe and leave a group.
One MBMS service includes one or more sessions and MBMS data is transmitted to a plurality of terminals (or user equipments) through a MBMS bearer service only when a session is ongoing. The system provides a MBMS bearer service to a terminal using a radio bearer. Radio bearer types used in the system are divided into a MTCH (MBMS Traffic Channel or Multicast Traffic Channel) and a MCCH (Multicast Control Channel). The MTCH, which is a logical channel, is configured for each MBMS service provided to one cell and is used to transmit user plane data to a plurality of terminals of a specific MBMS service. The MCCH, which is a logical channel, is used to transmit MTCH configuration (or setting) information or MBMS service configuration information in a cell to a terminal, in order to allow the terminal to receive service data through the MTCH.